Tech —

Ars System Guide: Small Form Factor systems

The Ars System Guide returns with a guide to building your own Small Form …

Going small

A functional computer does not need much to operate. Most users get by fine with a single hard drive, single optical drive, single CPU, single Ethernet interface, and often do not end up using their PCI slots thanks to the integration of just about everything onto modern motherboards.

A high-performance system often is not much more than what is listed above. Instead of onboard video, there's a single PCI-Express slot for a Geforce 7950 GX2, and instead of a more pedestrian 7200rpm hard drive, a 10,000rpm Western Digital Raptor fits in the exact same space as any other typical 3.5" hard drive. A single 5.25" expansion bay makes a standard-sized optical drive possible. A machine with the same capabilities as a full-sized desktop can now be repackaged in a small box, without the difficulties of sourcing special "small" and "low-profile" components that used to be commonplace.

Small Form Factor (SFF) represents the latest footprint for computers, one that allows them to be small enough to disappear from the desk, or the exact opposite: often considered attractive enough in their brushed-aluminum and anodized-black finishes with bright blue LEDs to be a showpiece of status.

One theme that kept coming to the forefront in our discussions of the hows and whys of SFF systems was that of sexiness. With their brushed aluminum, sleek black, or pearl white exteriors, SFF boxes have a certain visual appeal that other cases lack. So for some, the choice of an SFF system can be just as much about aesthetics as it is performance. With the multitude of SFF choices available, there is seldom any need to sacrifice performance for a looks.

Defining the SFF

A typical small form factor PC is not quite a cube. A shoebox is a better approximation of its size, or perhaps even a toaster oven. They can take the processor of your choice, have onboard video, sound, USB, Firewire, Ethernet, and often a pair of PCI-Express slots for a little bit of expansion. A single 5.25" bay and one or two 3.5" bays usually rounds things out. It is enough for a complete, full-featured system with very limited expansion.

The most common barebones SFF box today is a Shuttle, Iwill, or Biostar, all of which are similar in size, having roughly square dimensions in height and width and being somewhat longer. This allows for a small power supply of 200 to 350 watts and leaves enough room for a 80mm or 92mm fan in back for system and CPU cooling. A back panel full of VGA, USB, Ethernet, sound, and Firewire connectors provide a complete set of expansion opportunities. The front panels usually have USB, Firewire, and audio ports for additional expansion. Custom or semi-custom CPU heatsink/fan combinations are provided by most makers, with the most notable being Shuttle's heat-pipe with an 92mm exhaust fan. Two expansion slotsusually one PCI-e x16 and one PCImake it into most SFF systems. Vented side panels help keep high-end video cards cool, and the expansion slots usually have room for full-height cards so that the latest high-end video cards will fit.

SFF boxes outside of these dimensions are fairly common but less easily identifiable to the masses. Larger and smaller chassis, particularly super-slim ones and closer-to-cube-shaped ones are other common SFF shapes and sizes. Silverstone's SG-01, Antec's NSK1300, and Aspire's Q-Pack are well known examples of slightly larger SFF chassis that fit common microATX motherboards.

The other extreme is the extremely tiny system, a la the Mac mini. This goes into the realm of custom motherboards and chassis, based on laptop parts. The do-it-yourself SFF market does not go to this extreme, particularly due to the fabrication requirements and higher costs of using laptop parts compared to desktop parts.

One exposed 5.25" bay for optical drives sits at the front of a typical SFF box, with a handful of 3.5" bays below it. Vented front panels provide for some cooling, although with all of the drive bays stacked tight atop each other, typical SFF systems are not welcome places for those with hot-running multiple-hard drive setups. Some makers offer smaller and larger SFF chassis, such as Shuttle's P-series chassis. They're still small, but their being just a little bit larger or smaller than the typical SFF chassis often provides people with the exact size or expansion they need.

Due to their small size, SFF systems usually are not particularly quiet or cool as they are tightly packed with heat-producing components in close proximity. Condensing things into a chassis less than one-third the size of a typical mid-tower means this is an unavoidable consequence. With the exception of SFF system designed to be quiet, such as the Shuttle SB86i, most can become quite audible at full load. For most less-than-full load situations, careful tweaking of temperature-controlled fan settings often does the trick. A typical SFF box should be quiet enough for most users, provided they are not expecting complete silence.

Finally, SFF systems usually ship as barebones units (chassis, motherboard, power supply), due to their proprietary rear backplane layout. Packing everything inside such a small space has lead to extensive manufacturer customization of the motherboard and chassis. To compensate for this, most SFF makers have extensive SFF system lineups, covering chipsets from Intel, NVIDIA, ATI, SiS, and VIA, so you can pick and choose the SFF with the chipset and features that fits your needs.

Typical places for a SFF system

Budget desktop replacement: smaller and more attractive than a typical ATX or micro-ATX system, a small SFF box fits in some places that a regular ATX box would not. The limited expansion is not an issue because most people going this route don't need any additional expandability. Along with the Budget desktop replacement is the flexibility of putting a compact PC anywhere you need one. Some people use them a as a base for a "kitchen" box, providing access to recipes and other goodies right in the kitchen without sacrificing too much counter space.

Point-of-sale booths, display cases, etc: small, confined spaces where nothing else fits. It's often the only alternative is a laptop, which may not fit the allocated space and may cost more than a SFF. Alternatively, SFF enables many places to have a computer where they had none before without going to expensive custom industrial PC setups.

Portable Hot Rod: portability from the smaller size versus a regular ATX chassis makes a SFF Hot Rod attractive. SFF machines are lighter and more easily transported than full-sized systems, a huge advantage for gamers that move their systems frequently. The limited expansion still permits a full-height PCI-e card or two for high-end video, which means the SFF Hot Rod does not sacrifice any performance versus its standard-sized ATX brethren.

Home Theater PC (HTPC): small, attractive, and comes in lots of different color schemes to match your living room. The limited expansion room puts a crimp on those who would like to use their HTPC as a DVR, but it's certainly still possible. The two expansion slots can be filled with an PCI-e video/TV tuner card and the PCI slot with a high-end audio card, while USB wireless adapters make neat, clean networking installation possible.

Large clusters of SFF machines have been used to build supercomputers and other fairly exotic items. Others end up as servers. Indeed, there are many uses for SFF systems, where their small size substantially increases the versatility of where computers may go.

Small Form Factor and the System Guide

We cover two possible variations of the System Guide in a Small Form Factor format: the Budget Box and the Hot Rod.

With the ability to do a fully functional system inside a very small space, a SFF Budget Box makes a great deal of sense for those who need a computer that will fit into small spaces and be hidden away. People in small apartments, university dorms, and others who have space at a premium would probably appreciate such a system, although they're hardly the only ones.

The SFF Hot Rod is more for geek pride than it is for any real space advantage. Those who frequently move their computer may benefit more, but let us face it: a SFF Hot Rod is primarily a damned cool idea rather than an idea with roots in necessity.